An electrophotographic image forming apparatus forms a latent image on an electrophotographic photosensitive member, then develops the latent image with a development agent (hereinafter, referred to as “toner”) into a visible image and transfers the toner image to a recording medium through a transfer means to complete image formation. In such an electrophotographic image forming apparatus, a cleaning device removes extraneous matter, such as transfer-residual toner, from the electrophotographic photosensitive member, after the completion of transfer, in preparation for reuse of the electrophotographic photosensitive member.
FIG. 9 illustrates a photosensitive drum 100 and a cleaning device 600, after transfer processing by a transfer means. The photosensitive drum 100 moves in the direction of an arrow A, so that transfer-residual toner 001 left on the photosensitive drum 100, which has not been transferred during the transfer processing, reaches the cleaning device 600.
The cleaning device 600 includes a cleaning blade 601 having rubber elasticity, a toner housing portion 603 for housing extraneous matter, such as transfer-residual toner removed by the cleaning blade 601, and a sealing sheet 602 as a sealing member. The sealing sheet 602 contacts with the surface of the photosensitive drum 100 upstream of the cleaning blade 601 in the direction of the movement of the photosensitive drum, in such a manner as to allow the toner on the photosensitive drum 100 to pass therethrough in the direction of the movement of the photosensitive drum 100. The cleaning blade 601 removes the transfer-residual toner 003 that passes through a nip portion N between the sealing sheet 602 and the photosensitive drum 100, from the surface of the photosensitive drum 100. The sealing sheet 602 collects the removed toner 005 and causes it to be housed in the toner housing portion 603.
The aforementioned sealing sheet 602 is placed obliquely with respect to the photosensitive drum 100, such that the free end thereof is in contact with the outer peripheral surface of the photosensitive drum 100. Further, the sealing sheet 602 is placed, such that the gap between the photosensitive drum 100 and the sealing sheet 602 is gradually decreased in the direction of the rotation of the photosensitive drum 100.
As the aforementioned sealing sheet 602, a sealing sheet having elasticity is employed in order to prevent the occurrence of a gap at the nip portion N between the photosensitive drum 100 and the sealing sheet 602, and it is preferable to employ a sealing sheet 602 which can intimately contact the photosensitive drum 100. This is because a sealing sheet which can intimately contact the photosensitive drum can prevent the toner scraped off by the cleaning blade 601 from leaking to the outside of the toner housing portion 603 through the nip portion N between the photosensitive drum 100 and the sealing sheet 602.
There are sealing sheets made of thermoplastic urethane, which have been known as preferable sealing sheets (Patent Literature 1). It is preferable that the contact pressure between the sealing sheet and the photosensitive drum has a value which does not damage a photosensitive layer in the photosensitive drum and allows the toner on the photosensitive drum to pass through the nip portion N along with the movement of the photosensitive drum.
Patent Literature 1: Japanese Utility Model Application Publication No. 1-21323